1. Field of the Invention
The present invention relates to a light for an aircraft and, in particular, to an external light for an aircraft. While the present invention can be used primarily for each type of aircraft light, preferably the present invention is for a head light; taxi light, and runway turn-off light of an aircraft.
2. Description of the Prior Art
In the past, in the technical field of aerospace applications, light sources have been based on gas discharge technology or filaments. For several years, aircraft lights based on LED technology have found ever stronger commercial use. Examples for LED-based aircraft lights for different purposes are disclosed in U.S. Pat. No. 6,679,618, U.S. Pat. No. 7,572,030, US-A-2007/0164875, WO-A-2009/156349, EP-B-1 217 663, EP-B-1 264 767, EP-B-1 552 983, EP-B-1 836 437, and GB-B-2,350,176.
In order to fulfill the official requirements of the Federal Aviation Association (FAA) with regard to the spatial light intensity distribution based on LED technology, a plurality of LEDs have to be arranged. In these designs, the available space and cooling capacities are only two of several concerns to be dealt with in order to obtain a high intensity light.
From U.S. Pat. No. 1,275,120 a projecting apparatus is known in which an ellipsoid reflector is used for illuminating a slide or film, i.e. a two-dimensional surface is illuminated to be projected on a projection screen or the like surface. Such a projection apparatus cannot be used in a lamp in which the light has to be directed in a pre-determined special light intensity distribution as in case of an aircraft light.
From WO-A-2008/031405 there is known a reflector emitter for a strong light beam using a plurality of lower-power lamps, revolution-ellipsoid sections are formed from revolution ellipsoids which are additionally cut in the focal-point plane. The sectional planes of all the mirrors are arranged in one common base plane and the mirror surface f the further concave mirror is directed in the direction opposite the others. The light sources are arranged in the first focal points of the revolution-ellipsoid sections and their second focal points and the focal point of the further concave mirror coincide. All the light beams which are incident on the surface of the revolution-ellipsoid sections are reflected onto the further concave mirror. Here, the light beams form a shaped bundle which leaves the reflector emitter at right angles to the base plane through the aperture.
Moreover, in WO-A-2008/089324 a folded light path LED array collimation optic is described which relates to a compact optical assembly which improves collimation of light produced by multiple LED light sources in a light engine. A shaped primary reflector located over the light engine reflects the light toward a larger shaped secondary reflector. The shapes of the reflectors are selected to cooperatively produce a highly collimated light beam. Color mixing may be improved by providing a plurality of facets on the reflective surfaces of at least one of the primary reflector or the secondary reflector.
Due to limited spaces and weight limitations in aircrafts, it is often desirable to include several light functions in a single light. This is true e.g. for the landing light, taxi light, and potentially runway turn-off light (RTO) which typically are realized by different housings using relative large mounting spaces which in particular at the noise landing gear (NLG) is limited.